Heptasartorite is an extremely rare thallium-lead sulfosalt found almost exclusively in the famous Lengenbach Quarry in Switzerland. It typically occurs as small, lead-grey, heavily striated prismatic crystals associated with other complex sulfosalts in dolomite. Due to its extreme rarity and toxicity, it is sought primarily by advanced systematic mineral collectors.

Hardness

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareSartorite Group family

Heptasartorite

Hardness: 3
Luster: Metallic
Streak: Black
Transparency: Opaque

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Is this heptasartorite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch heptasartorite with a known reference. Heptasartorite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Heptasartorite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Heptasartorite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: lead-gray.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: striated prismatic crystals.

Often confused with

Heptasartorite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Sartorite

Mohs 3

How to tell apart: Streak differs, so Heptasartorite leaves black, Sartorite leaves chocolate-brown.

Often found alongside heptasartorite

Minerals reported to co-occur with heptasartorite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Tl₇Pb₂₂As₅₅S₁₀₈
Mohs hardness: 3
Density: 5.32 g/cm³
Colors: Lead-gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Striated Prismatic Crystals
Cleavage: Distinct On {010}
Rarity: Rare
Uses: Collector
Host rock: Dolomitic Marble of The Lengenbach Deposit
Typical price: $100-500+ per thumbnail specimen

Where rockhounds find heptasartorite

Classic worldwide localities

Lengenbach Quarry, Binntal, Switzerland

Field-hunting tip

Look in dolomitic marble of the lengenbach deposit country, the host setting where heptasartorite typically forms. If you start seeing realgar, orpiment, pyrite in float, you are in the right ground. Field specimens usually show a striated prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify heptasartorite?+

Mohs hardness is 3. It typically shows a metallic luster. The streak is black. Common colors include lead-gray.

Where is heptasartorite found?+

Notable localities include Lengenbach Quarry, Binntal, Switzerland.

How much is heptasartorite worth?+

Typical asking prices fall in the range of $100-500+ per thumbnail specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is heptasartorite safe to handle?+

It contains toxic constituents. Contains thallium and arsenic; handle with gloves, avoid inhaling dust or ingesting particles, and wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like heptasartorite?+

Heptasartorite is most often confused with Sartorite, Gratonite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with heptasartorite?+

Heptasartorite commonly co-occurs with Realgar, Orpiment, Pyrite, Sartorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does heptasartorite form in?+

Heptasartorite typically forms in dolomitic marble of the lengenbach deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is heptasartorite used for?+

Heptasartorite is used in collector.

Find heptasartorite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.